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Патент USA US2408102

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.Sept. 24, 1946.
2,403,101 '
Filed July 11, 1942
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Patented Sept.‘ 24, 1946.
I‘ ,
{2,408,101 ._
~ uurrgo sTATa's' PATENT om¢E-_~ j
Ober c. swim-beck, Rahway, N. 1., assignor to
Standard Oil Development Company, a corpo
ration of Delaware
Application July 11, 1942, Serial N0.r450,519
6 Claims.
(Cl. 204-—77)
The present invention pertains to a method of
preparing vicinal glycols by electrolytic'reductlon I
- of 'ketones and generally to all types of carbon
to carbon reductive condensation reactions.
Speci?cally, this invention is concerned with
the reduction of acetone electrolytically to tetra
' methylethylene glycol.
toxic lead alkyls which‘diminish the effective
'ness of the cathode can be minimized and the '
reduction oi ketones to viclnai glycols effected
with good vcurrent emciency and high ratio of
glycols to other reduction products by utilizing
as the cathode sheets of copper or other metal
of low hydrogen overvoltage' coated with zir
conium. In-contrast to lead, which tends to
It is the ‘object of the present invention to
form insoluble lead alkylsiduring the electroly
provide the art with a novel and highly advan
tageous method of electrolytically forming vicinal 10 sis, which alkyls coat the cathode and rapidly di
minish the eifectivenessof the cathode, the zir-,
glycols and especially pinacol from the corre
conium coating on the cathode forms zirconyl
sponding ketone, and also to provide the art with
sulfate which is soluble in the catholyte and
novel electrodes for effecting the reduction of
Organic compounds.‘
therefore does not coat or impair the eiiiciency
The electrolytic reduction of ketones can take 15 of the cathode.- The zirconium coating can be
easily applied to the low hydrogen/overvoltage
place at the cathode surface according to any
metal by electrolysis.,
one of the following reactions:
Deposits of metallic zirconium were obtained
from an aqueous complex sulfate bath substan
20 tially in accordance with the conditions described
by Brandt ‘and Linford, Trans. Electrochem, Soc.
70, 431 (1936). The conditions used by appiican
were as follows:
Anode: Platinum sheet. ~
Cathode: Buifed and cleaned copper sheet.
Electrolyte: Produced by converting 18.0 g. of
ZrOa' to thevsulfa'te, dissolving in 100 cc._ of 0.5
CH3 + 1130
M. NaaSOa solution and diluting to 500 cc.
Current density: 0.12-0.-2 amp/cm’. '
Other side reactions result in the formation of
Temperature: 20° C.
metal alkyls, especially when the reduction is ef
Total current passed: One ampere-hour. '
fected in acid medium with lead cathodes. ‘
An electrolytic method for effecting the.- reduc
tive condensation reaction whereby acetone is
It is preferred to applya zirconium coating to
the low hydrogen overvoitage metal base in such
converted to pinacol using a lead cathode and an 35 thickness that it weighs from about 0.01 to about
acid catholyte is described in German Patent
113,719 (1899).
Several German patents pertaining to the'elec
trolytic reduction of acetone to pinacol were issued in the period 1912-1920. Among these were
0.5 g./sq. dm.
The ketones which may be treated in accord
ance with the present inventioncorrespond to
- the general formula
D. R. P. 306,304 (1917), 806,523 (1918) and 324,919
-( 1920) . The principal developments made in this
period appear to have been the use of mixed
metal and alloy cathodes, such as 4 to 10% cop
per-96 to 90% lead mixtures and 10% tin-90%
lead alloy, and the use of horizontally suspended
cathodes to prevent the metal alkyls formed from
accumulating on and decreasing the activity of
v the electrode surface.
All of the prior processes for electrolytically
the R's'stand for a member of the group
48 wherein
consisting of alkyl ‘and aryl radicals and alkyl
and aryl radicals substituted by, a group which is
not reducible under the conditions employed, 1. e.,
halogen, carboxyl, etc. Such ketones include, for
to example acetone, methyl ethyl ketone', diethyl
ketone, methyl propyl ketone, ethyl propyl ke- .
converting acetone to tetramethylethylene glycol
tone,'_acetophenone and benzophenone. .
have been unsatisfactory either because pinacol
By using mixtures‘ of different ketones, it is
current e?iciency or the overall current e?lciency _.
‘possible to prepare certain mixed glycols. For
or both were too low. y
example,‘ acetone mayv be condensed with methyl
It has now been found that the formation of
_ ‘l,
2,408,10 1
the formula
ever, may vary in strength between about 15%
and about 40%. The acid strength indicated is
percentage by weight.
The anolyte may be a sulfuric acid solution of
about 15 to 40% strength.
or methyl ethyl ketone may be condensed for ex
ample with acetophenone to form theglycol
furic acid of about 20% strength. The acid, how
ethyl ketone to form the glycol corresponding to
The electrolyte is
preferably maintained at temperatures between '
about 0° C. and about 25° C. The current density
applied may vary between about 0.1 and about
10 4.0 amperes/sq. din", the preferred current den
sity being within the range of about 1 to about 2
The following example serves to illustrate my
The glycols formed in accordance with the
inventionv but it is to be understood that my in
present invention correspond to the general for
15 vention is not limited thereto.
Example 1
3% liters of a 4/1 acetone-20% sulfuric acid
\C-CK .
solution were placed in the cathode compart
ment of a cell as shown in the drawing.
wherein each R stands for an alkyl or aryl radi 20 anolyte used was 25—40% sulfuric acid and the
anode was lead. The cathodes used are copper
cal or an alkyl or aryl radical substituted by a
substituent such as halogemgcarboxyl, ‘etc.
sheets onto which zirconium was electroplated
A cell suitable for carrying *out ~the reduction
from an aqueous solution of zirconyl sulfate and
of ketones in accordance with thepresent inven
sodium sulfate as described above.
tion is shown diagrammatically ‘in the accom 25.
panying drawing.
Electrolysis was effected at about 10° C. at a
current density of 1.0 amperes/ and at
Fig. l is a plan view, partly‘inrsectionrof a sin-_
.6-8 volts. The run was continued for 3 hours and
a total'of 24 ampere hour-s were supplied to the
gle unit cell, and
6811. Upon conclusion of the electrolysis the
Fig. 2 is an isometric view of the cathode of
the present invention with part of the coating
catholyte was stripped of isopropyl alcohol and
unreacted acetone and pinacol (tetramethyl
The single unit cell shown consists of a rec
ethylene glycol) was separated as the hexahy
tangular jar or the like ‘0 arranged in a cooling
bath a. An anode e,of lead or the like is ar
drate by cooling and ?ltering the stripped cath
olyte. 24.8 grams of pinacol hydrate and 2 grams
which diaphragm divides the» cell into an anode
to a current e?iciency based upon pinacol of 24%.
The ratio of pinacol hydrate to isopropyl alcohol
ranged inside an acid resistant diaphragm d_ 35 of isopropyl alcohol were obtained corresponding
and cathode compartment. As shown, 2 cathodes
0 having a zirconium coating thereon are ar
ranged in the cell. '
was 12.4/ 1. There ‘was no metal alkyl formation .
on the cathode.
The details of the cell are not critical to my 40
What I claim and desire to'secure by Letters
invention and the cell may be altered in numer
Patent is:
ous ways. For example, a number of cells could
1. In the process of producing glycols corre
be combined in a single tank and if desired the
sponding to the general formula
process could be carried out continuously by pro
viding a circulating pump, an overflow means for
drawing o? thecatholyte from the cell, means
for separating electrolysis products from‘ the
withdrawn catholyte and means, for making the
wherein R stands for a member of the group con
catholyte up to initial strength for reintroduc
sisting of alkyl and aryl' radicals and substituted
tion into the cell.
alkyl and aryl radicals by the electrolytic reduc
R/hn hH\R
Fig. 2 illustrating the electrode in‘accordance
with the present invention has part of the zir-v
tion of an aqueous acid solution of a ketone of
the formula
conium coating removed to show the base.
The use of a‘ diaphragm is recommended since
the products formed at the cathode are liable to 56
be oxidized at theanode. The use of a diaphragm
may be avoided if desired however by the use of
wherein R stands for a member of the group con
anolyte and catholyte of unequal densities, in cells
sisting of alkyl and aryl radicals and alkyl and
provided with horizontal electrodes, the use of a
' aryl radicals substituted by a group which is not
high anodic current density or by the use of 60 reducible under the reaction conditions, the im
anodes having a low oxygen overvoltage, i. e.,
nickel or by a combination of two or more of these
provement which comprises e?ecting the said re
duction at a cathode consisting of copper coated
Aside from the nature of the cathode surface,
the factor which has the greatest effect upon the 05
with zirconium.
2‘. The process of producing tetramethylethyl
ene glycol which comprises subjecting a solution
of acetone in an aqueous acid solution containlns
about 15 to 40 wt. per cent of sulfuric acid to elec
have given the best results. The ratio of ketone
lytic reduction at a current density of between
to water in the catholyte' should be high. How
ever, a ratio of 4/1 appears to be approximately 70 about 0.1 and 4~amperes per sq. dm. at a tem
perature between about 0° C. and about 25° C. in
' the upper limit economically because of the‘ high
contact with a cathode consisting of copper coat
resistivity of the solution which would greatly
‘ ed with zirconium.
increase the power cost. ‘In the production of
3. The process of producing tetramethylethyl
pinacol the preferred catholyte is one containing
about 4 volumes of acetone for each volume of sul 15 ene glycolwhich comprises subjecting a solution
course of the reaction in the cell is the concen
tr. ion and type of electrolyte vused. Acid media
of about \4 parts by volume of acetone in 1 part
by volume of an aqueous solution of sulfuric acid
of about 20 wt. percent strength to electrolytic
reduction at a current density of between about .
1 and 2 amperes per sq. dm.; in a diaphragm cell
at a temperature between about 0° and 425° C. in
contact with a cathode of copper coated wlthzir-l
4. The process as de?ned in claim '1 wherein
‘the zirconium coating on the cathode weighs
about 0,01 to about 0.5 g./sq. dm.
5. The process as de?ned in claim 2 wherein
the zirconium coating on the cathode weighs
about 0.01 toabout 0.5 g./sq. dm.
6. The process as de?ned in claim 3 wherein
the zirconium coating on the cathode weighs
about 0.01 to about 0.5 gJsq. dm.
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